This is a list of telephone dialling codes in the United Kingdom. The national telephone numbering plan is maintained by Ofcom, an independent regulator and competition authority for the UK communications industries. This list is based on the official standard, but includes defunct codes and historical changes, including the derivation of the two letter identities, in cases where known. The United Kingdom adopts an open telephone numbering plan for its public switched telephone network. Dialling codes do not correspond to specific political boundaries. For example, the Coventry dialling code covers a large area of Warwickshire and the Manchester dialling code covers part or all of several neighbouring towns.